Strain-Induced Band-Edge Modulation in Lead-Free Antimony-Based Double Perovskite for Visible-Light Absorption

Herein, we synthesized Sb-based single crystals (SCs) of Cs2AgSbCl6 with an impressive low bandgap of ∼1.82 eV and demonstrated the effect of strain on optical properties. Interestingly, the polycrystalline ground powder and the heated SCs of Cs2AgSbCl6 exhibited a larger bandgap of ∼2.55 eV. The reduction of bandgap is attributed to the existence of strain in the SC as confirmed by X-ray diffraction and Raman spectroscopy and supported by density functional theory (DFT) calculations. The strain engineering for bandgap reduction can play a pivotal role for developing low-bandgap lead-free double perovskite for environmentally friendly solar cell applications.